I am a theonomist and I will not deny that my ethics are theonomic they are God's Ethics and God's Law Word. However, that does not mean I agree that the death penalty is just for all of the usual suspects of law breaking other theonomists might. I do, however, agree that all categories are law breaking the Cosmic Law of God. Which might seem extreme as well.
However, whatever goes against God's Moral Law is law breaking and the Cosmic nature of God means that His law is universal, absolute, unchanging and yes arbitrary on His Creatures. Thus we will be under it until Christ Returns and The Final Judgment takes place.
This means all Nations are obligated to keep God's Law Code wherever it is not altered in the New Testament. Wherever it is not stated it has changed it is the same and the Moral Law will never change it is absolute and Eternal as God is. Which means we should be in constant prayer for Nations to come to Christ, recognizing Him as Lord and governing according to His Laws not man made ones.
I consider myself a kinder and gentler theonomist and a kinder gentler Reconstructionist. I wish for Nations to come to be Christian Nations and for leaders to follow God's Law Word. However, I realize it is not I or any other Reconstruction proponent that will bring that about only God he hearts of the civil magistrates. This is why I do not push the issue with people at my Church.
I take Unity in the True Faith as coming before uniting in theonomy or any other more divisive topic. That does not mean I think God's Law for the modern day is not an important part of one's Obedience to God for His Saving Grace. I absolutely do and think often the extreme anti theonomic folks take things too far to the other extreme of Law not having any use.
At the end of the day though we are all part of the Blood Bought Family of God and our views on eschatology and political visions should not separate family from loving and caring for one another.